Cool build, I would agree, he was basically explaining part of the battery management system when he was showing the magnetic latch relay for the battery.
Home Assistant is definitely a relatively easy way to integrate software control in the scheme of things, and has tons of potential. I am always leery of having single points of control and liked to implement a software option that runs in parallel an actual hard wired solution. It is very possible some of that is there, I just didn't see it.
I like the mixture of 80/20 and wood.